Question about deadlocks

[kiros88]

So I just want to clarify this before attempting to do multithread program. If I were to have 2 threads run simutaneously. And both of them are going to access the same QUEUE which is going to be mutex locked. Since both of them are going to fill the Queue up. Would this cause a deadlock and I would need pthread conditions to avoid deadlocks or will the mutex function cause the other thread to just wait until it becomes unlocked?

[bithub]

No, it would not cause a deadlock. You will not need condition variables, just a mutex.

[kiros88]

So just to be sure since one thread locks the queue to access it would hte other thread just be in a wait state until the queue is unlocked and available for the next thread

[bithub]

yes, the other thread would wait until the first thread unlocks the mutex.

[Elysia]

A deadlock occurs when both threads are waiting on a lock held by other threads that potentially waits on something else. Example:
There are two locks: A and B.
There are two threads: A and B.
Thread A executes and locks Lock A.
Thread B executes and locks Lock B.
Thread A executes and tries to lock B. But B is already locked by Thread B, so it falls into a waiting state.
Thread B executes and tries to lock Lock A. But Lock A is already locked by Thread A, so it falls into a waiting state.
Since neither state will ever unlock the locks that the respective threads are waiting for, nothing will ever happen. This situation is called a Deadlock.

But in your case, you can see this situation will never happen. It should never happen if the multi-threaded programming is done right.

[iMalc]

In certain circumstances a thread can also deadlock with itself. But Yeah Elysia has described the classic deadlock.

My question would be that if two threads a filling a queue up, where is this data going? Wont some thread taking data out of the queue also at some point?